Rashi: It seems to me that they kill me. So is shut up in my bones, what my tormentors anger and revile me.

Radak: When they say to me "where is your G-d?", it is as if they mortally strike my bones. 'If He is Elokim, why does He leave you in exile?!' It is as if each one of them stabs me with a sword and kills me. The bones are the foundation of the body. "B'Retzach" is To'ar (adjective) for the sword with which they kill.

Malbim: It is the hidden, inner murder, via their saying "where is your G-d?" Why does He not do for you miracles, like in days of old?!